Digital Laser Diode Driver Interface Enhances SFP+ Optical Module Controller

Jan. 31, 2011

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SFF-8472 standard

The small-form-factor pluggable (SFP) module is probably the most popular optical transceiver format for both data communications and telecommunications applications. These transceivers run at data speeds to 10 Gbits/s, so they’re a challenge to implement. Now, Maxim Integrated Products is making life easier for designers of SFP modules by introducing the DS1878, a small-form-factor pluggable plus (SFP+) controller with a digital laser diode driver (LDD) interface. State-machine-based, the DS1878 eliminates the need for software development. It enables efficient implementation of the SFF-8472 specification and greatly reduces time-to-market.

The SFF-8472 standard defines digital monitoring and diagnostics functions. The DS1878 implements these controls and monitors all functions for small-form-factor (SFF), SFP, and SFP+ optical modules and fully supports the SFF-8472 standard (see the figure). It can be combined with a MAX3798 or MAX3799 SFP+ laser driver/limiting amplifier to provide an automatic power control (APC) loop, modulation current control, and eye safety functionality—the core feature set of SFP and SFP+ optical modules. The DS1878 also works with the MAX3945 limiting amplifier or the MAX3946 LDD to support 10-GHz applications featuring distributed feedback (DFB) or electro-absorption-modulated (EML) lasers.

Laser modulation is controlled with a dedicated temperature-driven lookup table (LUT). Two additional 9-bit delta-sigma digital-to-analog converter (DAC) outputs with 36-entry LUTs are provided. The DS1878 monitors six analog channels: temperature, VCC, and MON1 to MON4, which can be used to monitor laser current, optical output power, and optical input power.

The DS1878 is specified from –40°C to 95°C. It uses 0.35-μm technology to enable the high level of integration required for SFF-8472 implementation in a small 5- by 5-mm, 28-pin thin quad flat no leads (TQFN) package with exposed pad. Pricing begins at $1.33 in 1000-unit quantities.

Maxim Integrated Products

About the Author

Lou Frenzel | Technical Contributing Editor

Lou Frenzel is a Contributing Technology Editor for Electronic Design Magazine where he writes articles and the blog Communique and other online material on the wireless, networking, and communications sectors. Lou interviews executives and engineers, attends conferences, and researches multiple areas. Lou has been writing in some capacity for ED since 2000.

Lou has 25+ years experience in the electronics industry as an engineer and manager. He has held VP level positions with Heathkit, McGraw Hill, and has 9 years of college teaching experience. Lou holds a bachelor’s degree from the University of Houston and a master’s degree from the University of Maryland. He is author of 28 books on computer and electronic subjects and lives in Bulverde, TX with his wife Joan. His website is www.loufrenzel.com.